mget empty strings

Dear R community,

I am a beginner to R and have a question concerning mget, about I could 
not find anything in the various documentation.

I have a column in a dataframe x for which I want to get values in y:

mget(x[,1], env=y, ifnotfound=NA)

I receive an error mesage:

Error in mget(x[, 1], env = y, ifnotfound = NA) :
         attempt to use zero-length variable name

this is probably due to the fact that some of the values in x[,1] are 
empty ("")

I would like to get a "NA" for these values, and the found value for 
those where mget finds one. Could anyone tell me how this is done 
efficiently?

Thanks a lot in advance!

Georg


P.S. I am in digest mode, cc'ing the answer directly to me would be nice

Georg Wilhelm Otto
Max-Planck-Institute for Developmental Biology
Spemannstrasse 35/III
D-72076 Tuebingen Germany
phone: +49-7071-601 401
http://www.eb.tuebingen.mpg.de